Modern respirators (also known as ventilators) are characterized by increasing complexity of monitoring and supply of the patients. They have monitoring units, which record a great variety of variables, for example, airway pressures, breathing gas concentrations or oxygen saturations of the patient's blood. The monitoring units of the respirators check the measured values within the set limit values and inform the user in case of changes. In more modern respirators, the monitoring units of the respirators are equipped with intelligent algorithms, which automatically recognize whether a certain variable to be monitored shall be monitored. It is detected for this, for example, whether a sensor necessary herefor has been connected to the patient and whether it is providing corresponding measurement results. It is only after all the criteria necessary for monitoring the variable to be monitored have been met that the monitoring unit is activated. If, for example, a patient is connected to a respirator in an ambulance, the oxygen saturation of the blood (SPO2 value) is thus monitored only after a sensor for measuring the SPO2 value of the patient has been connected and the monitoring unit has detected the pulse of the patient. If the patient is connected to another, second respirator after transport into an operating room of a hospital, the SPO2 value is monitored again only when the monitoring unit has recognized a sensor connected to the patient and has recognized a pulse from this patient. However, if the patient's status has considerably exacerbated at the time of the changeover between the respirators or if one has forgotten to connect the pulse monitoring, so that no pulse has been able to be recognized by the monitoring unit, no monitoring of the SPO2 measurement takes place because of the automatic monitoring control. No alarm is triggered for the user for the lack of SPO2 measurement and/or the exacerbated state of the patient. This state may lead to a worsening of the patient's status.